The city is cracking down on shady employment agencies that prey on people desperate for work by demanding cash up front for interviews or applications for nonexistent positions, The Post has learned.

The Department of Consumer Affairs has fired off 115 subpoenas and has begun investigating 23 employment agencies that allegedly have a history of pulling con jobs.

A 25-year-old Brooklyn woman named Jessica charged she was scammed by NYC Empire Security Multi-Services when a representative promised her a bartending job after she completed mixology training for $300. The agency gave her an hour-long course and then handed her a paper that read, “Certified Mixologist,” she said.

She was then allegedly told that interviews had been arranged at Gaslight in the Meatpacking District and at the strip club FlashDancers in Midtown. Gaslight refused to talk to her and FlashDancers said it had never hired the agency, she said.

She never got a refund.

“Because I was desperate for work, I agreed to pay the fee,” Jessica said in an affidavit for the DCA. “[The agency] would only accept payment in cash.”

Five complaints were filed against NYC Empire Security since 2013.

“Many of the bad actors in this industry prey on the most vulnerable — New Yorkers with low incomes, immigrants and young people,” DCA Commissioner Julie Menin said.

“These agencies make promises of jobs that don’t exist and often charge illegal fees or refuse to give refunds. For someone unemployed or trying to make a better living . . . these fees can deplete their savings, leaving them with nothing.”

Rosa, of Ecuador, complains she was cheated by United Employment Agency in Jackson Heights, which allegedly promised her a job in a laundromat in exchange for $125 in cash.

But the laundromat did not exist, she said.

When she asked for another interview or her money back, she was told that she didn’t get the job because she was too old.

“I never received my money,” Rosa said. “The lady said, even if I cried blood, ‘I’ll never give it to you.’ ”

The DCA received seven complaints against that agency since 2011.

Calls to owners or lawyers for the agencies — both of which are being probed by the DCA — were not immediately returned.